[PATCH v4 01/10] loop: Factor out loop size validation

[Martijn Coenen]

Ensuring we don't truncate loff_t when casting to sector_t is done in
multiple places; factor it out.

Signed-off-by: Martijn Coenen <m...@android.com>
---
 drivers/block/loop.c | 25 ++++++++++++++++++++-----
 1 file changed, 20 insertions(+), 5 deletions(-)

diff --git a/drivers/block/loop.c b/drivers/block/loop.c
index f1754262fc94..396b8bd4d75c 100644
--- a/drivers/block/loop.c
+++ b/drivers/block/loop.c
@@ -228,15 +228,30 @@ static void __loop_update_dio(struct loop_device *lo, 
bool dio)
                blk_mq_unfreeze_queue(lo->lo_queue);
 }
 
+/**
+ * loop_validate_size() - validates that the passed in size fits in a sector_t
+ * @size: size to validate
+ */
+static int
+loop_validate_size(loff_t size)
+{
+       if ((loff_t)(sector_t)size != size)
+               return -EFBIG;
+
+       return 0;
+}
+
 static int
 figure_loop_size(struct loop_device *lo, loff_t offset, loff_t sizelimit)
 {
+       int err;
        loff_t size = get_size(offset, sizelimit, lo->lo_backing_file);
-       sector_t x = (sector_t)size;
        struct block_device *bdev = lo->lo_device;
 
-       if (unlikely((loff_t)x != size))
-               return -EFBIG;
+       err = loop_validate_size(size);
+       if (err)
+               return err;
+
        if (lo->lo_offset != offset)
                lo->lo_offset = offset;
        if (lo->lo_sizelimit != sizelimit)
@@ -1003,9 +1018,9 @@ static int loop_set_fd(struct loop_device *lo, fmode_t 
mode,
            !file->f_op->write_iter)
                lo_flags |= LO_FLAGS_READ_ONLY;
 
-       error = -EFBIG;
        size = get_loop_size(lo, file);
-       if ((loff_t)(sector_t)size != size)
+       error = loop_validate_size(size);
+       if (error)
                goto out_unlock;
        error = loop_prepare_queue(lo);
        if (error)
-- 
2.26.2.303.gf8c07b1a785-goog